The red line in the not-very-good image that I’ve amended shows (very approximately!) the route that would need to be dredged to allow access to the cruise terminal (Terminal Marittima) if cruise ships were required to enter the lagoon via the southern entrance at Malamocco. The light-blue areas in the diagram are the currently-navigable channels. Passenger ships, including cruise ships, currently access the lagoon at the right-hand side via the Ingress Passageri through the Bocca di Lido. Then (as you can see) they pass immediately to the south of the city, and to the north of Giudecca, towards the passenger terminal in the west of the city. Cargo ships enter the lagoon via the southern entrance (“Bocca di Malamocco”), navigate westwards until they reach the mainland, then north to the commercial port at Maghera.

What is needed, and what has apparently been agreed in principle, is a new deep-water channel leaving the cargo-ship channel part-way to Maghera and heading towards the passenger terminal. That’s what the red line indicates, though please note that this diagram isn’t in any way a plan of where any route will actually be dredged: it’s just to show the general positions.